My wife and I were up to Barrie for a weekend in March to visit our son and his fiancée. While the women folk were out looking a bridal gowns, my son and I headed up to Midland to visit the Wye Marsh. It's only 40 minutes from Barrie as opposed to 2 hours from Markham.
When we arrived, we discovered that it was the Sweetwater Harvest Festival which include entry to both the Wye Marsh and Sainte-Marie among the Hurons. Bonus and not very crowded.
"Spring is in the air! Join the Friends of Wye Marsh and Sainte-Marie Among the Hurons for a celebration of the spring season and all things maple syrup! Wander through the sugar bush and visit the sugar shack to watch sap being turned into liquid gold. Roast Bannock on a fire, visit the birds of prey, check out historical demonstrations and swing by the Sweetwater Arts & Crafts Market! "